Department of Fisheries and Wildlife
 

Defense Coastal Estuarine Research Program: Understanding the Top-down and Bottom-up Influences on Shorebird Productivity, Survival, Habitat Use, Foraging Dynamics and Demography in Relation to Beach Management Practices on MCBCL.


widllife picture

We will study (from left to right) Wilson's plovers, a diversity of mesopredators (red fox shown here) and Willets ( Bill Schmoker) on the barrier islands at Camp Lejeune, North Carolina.

Project Background:  My lab and Jim Fraser’s lab here at VT are part of an interdisciplinary team of scientists studying the function of the coastal ecosystems at Marine Corps Base Camp Lejeune, North Carolina.  See DCERP for more information on all of the projects that are a part of the Defense Coastal Estuarine Research Program. We are part of the Coastal Barrier Island module and are collaborating closely with Drs. Pete Peterson and Antonio Rodriquez and their students at the University of North Carolina Institute of Marine Sciences on the following project.

Barrier islands provide key habitats for nesting, migrating, and wintering shorebirds. Many shorebird species are declining worldwide due to a variety of factors stemming from habitat degradation and loss. A number of shorebird species use the MCBCL (see Table below), including the threatened piping plover (Charadrius melodus) and the ESA candidate species, the red knot (Calidris canutus rufa). Under the ESA, MCBCL is required to use its authorities to further the conservation of the piping plover and may soon be required to do the same for the red knot.  Moreover, under a recently signed Memorandum of Understanding (MOU) (71 Federal Register 51580-51585), DoD agreed to work with the FWS to step up its protection of migratory birds, including taking actions to minimize take, to identify and protect key habitats, and to prevent damage to such habitats.

A key to successful conservation and management of shorebirds and other migratory birds at the MCBCL is a detailed understanding of whether shorebird populations that use the barrier island system are more greatly limited by top-down (e.g., predation) or bottom-up processes (e.g., food availability and sedimentary habitat). On coastal barrier islands with heavy human use, predation by meso-predators (e.g., foxes, raccoons, feral cats) has been demonstrated to often be the most important factor affecting shorebird productivity, survival, and distribution (e.g., Patterson et al., 1991). Prey community structure (e.g., abundance by species, size class distribution) and availability is also frequently identified as an important factor limiting avian use of an area on migratory stopover, nesting success, and over-winter survival (Newton, 2005), and experimental studies have demonstrated that foraging shorebirds can alter the composition of invertebrate prey communities (Quammen, 1981, 1984). Finally, in addition to the biologically mediated top-down and bottom-up processes of predation and food limitation, physical forces can structure coastal shorebird communities. The morphology of coastal barrier islands is extremely dynamic and at any given moment reflects a temporary balance between geology and physical forces. Washover fans, for example, typify barrier islands in a wave-dominated setting that are undergoing long-term transgression or possibly the recent impact of a severe storm. Understanding the historical trends and predicting future washovers is important for management strategies of biota using this habitat and long-term sediment budgets. Bay side intertidal flats formed and maintained by these washovers are key habitats for migrating and resident shorebirds and seabirds. Piping plover nesting density and nesting success often are greatest on beaches adjacent to such flats. Wintering piping plovers forage on bayside intertidal areas in preference to the ocean swash zone whenever bay flats are available (Loegering and Fraser, 1995, Fraser et al., 2005;). Other species, such as ruddy turnstones, willets, sanderlings and red knots also forage extensively in these habitats (Karpanty et al., 2006).

Once the relative importance of top-down and bottom-up processes on the abundance, survival and productivity of key shorebirds is known, then the Base’s INRMP can be revised to use resources most efficiently to manage limiting factors to best meet the intent of the ESA and this new MOU (e.g., control predators versus supplement food availability versus create washover habitats).

Technical Objectives/Goals:

  1. To understand the biotic and abiotic variables that drive shorebird reproductive output and breeding season distribution on MCBCL.
  2. To relate trends in shorebird foraging and nesting distributions, abundance, and reproductive output to variation in land use (e.g., military training versus recreation versus no present human activities with attention to frequency and duration of specific activities in each category) and management practices (e.g., beach closures, ORV regulations, restricted military or recreation activities, potential beach replenishment, vegetation control, dune rebuilding) so that (1) shorebird indices may be used as indicators of ecosystem function, and (2) the best and most efficient management and monitoring can be applied.
  3. To understand those elements of predator ecology on barrier islands needed to enhance shorebird conservation and most efficiently control predators as needed.


Selected Shorebirds/Seabirds that Use MCBCL and Their Status

Species

Nester

Migrant

Status

Piping plover

X (potential)

X

Federally threatened

Red knot

 

X

Federal candidate species

Wilson’s plover

X

X

High concern (North American Shorebird Plan)

American Oystercatcher

X

X

High concern (North American Shorebird Plan)

Sanderling

 

X

Possibly declining

Black-bellied plover

 

X

Common

Semipalmated sandpiper

 

X

Common

Semipalmated plover

 

X

Common

Least tern

X

X

Possibly declining